172 BIRDS OF AUSTRALIA. 



" The mounds differ very much in their composition, form, 

 and situation : most of those that are placed near the water's 

 edge were formed of sand and shells without a vestige of any 

 other material, but in some of them I met with a portion of 

 soil and decaying wood ; when constructed of this loose ma- 

 terial they are very irregular in outline, and often resemble a 

 bank thrown up by a constant heavy surf. One remarkable 

 specimen of this description, situated on the southern side of 

 Knocker's Bay, has the appearance of a bank, from twenty-five 

 to thirty feet in length, with an average height of five feet ; an- 

 other even more singular is situated at the head of the harbour, 

 and is composed entirely of pebbly iron-stone, resembling a 

 confused heap of sifted gravel ; into this I dug to the depth of 

 two or three feet without finding any change of character ; it 

 may have been conical originally, but is now without any 

 regularity, and is very extensive, covering a space of at least 

 a hundred and fifty feet in circumference. These remarkable 

 specimens would, however, seem to be exceptions, as by far 

 the greater number are entirely formed of light black veget- 

 able soil, are of a conical form, and are situated in the densest 

 thickets. Occasionally the mounds are met with in barren, 

 rocky and sandy situations, where not a particle of soil similar 

 to that of which they are composed occurs for miles round : 

 how the soil is produced in such situations appears unac- 

 countable ; it has been said that the parent birds bring it 

 from a great distance ; but as we have seen that they readily 

 adapt themselves to the difference of situation, this is scarcely 

 probable : I conceive that they collect the dead leaves and other 

 vegetable matter that may be at hand, and which decomposing 

 forms this particular description of soil. The mounds are 

 doubtless the work of many years, and of many birds in suc- 

 cession ; some of them are evidently very ancient, trees being 

 often seen growing from their sides ; in one instance I found 

 a tree growing from the middle of a mound which was a foot 

 in diameter. I endeavoured to glean from the natives how 



